Question: Simplify the following expression: $p = \dfrac{1}{5r} + \dfrac{3}{7r}$
In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5r$ and $7r$ $\lcm(5r, 7r) = 35r$ $ p = \dfrac{7}{7} \cdot \dfrac{1}{5r} + \dfrac{5}{5} \cdot \dfrac{3}{7r} $ $p = \dfrac{7}{35r} + \dfrac{15}{35r}$ $p = \dfrac{7 +15}{35r}$ $p = \dfrac{22}{35r}$